The present invention relates to methods and devices for closing a body lumen, tissue opening, or cavity and, in particular, for closing an atrial septal defect.
Embolic stroke is the nation""s third leading killer for adults, and is a major cause of disability. There are over 700,000 strokes per year in the United States alone. Of these, roughly 100,000 are hemoragic, and 600,000 are ischemic (either due to vessel narrowing or to embolism). The most common cause of embolic stroke emanating from the heart is thrombus formation due to atrial fibrillation. Approximately 80,000 strokes per year are attributable to atrial fibrillation. Atrial fibrillation is an arrhythmia of the heart that results in a rapid and chaotic heartbeat that produces lower cardiac output and irregular and turbulent blood flow in the vascular system. There are over five million people worldwide with atrial fibrillation, with about four hundred thousand new cases reported each year. Atrial fibrillation is associated with a 500 percent greater risk of stroke due to the condition. A patient with atrial fibrillation typically has a significantly decreased quality of life due, in part, to the fear of a stroke, and the pharmaceutical regimen necessary to reduce that risk.
For patients who develop atrial thrombus from atrial fibrillation, the clot normally occurs in the left atrial appendage (LAA) of the heart. The LAA is a cavity which looks like a small finger or windsock and which is connected to the lateral wall of the left atrium between the mitral valve and the root of the left pulmonary vein. The LAA normally contracts with the rest of the left atrium during a normal heart cycle, thus keeping blood from becoming stagnant therein, but often fails to contract with any vigor in patients experiencing atrial fibrillation due to the discoordinate electrical signals associated with AF. As a result, thrombus formation is predisposed to form in the stagnant blood within the LAA.
Blackshear and Odell have reported that of the 1288 patients with non-rheumatic atrial fibrillation involved in their study, 221 (17%) had thrombus detected in the left atrium of the heart. Blackshear J L, Odell J A., Appendage Obliteration to Reduce Stroke in Cardiac Surgical Patients With Atrial Fibrillation. Ann Thorac. Surg., 1996.61(2):755-9. Of the patients with atrial thrombus, 201 (91%) had the atrial thrombus located within the left atrial appendage. The foregoing suggests that the elimination or containment of thrombus formed within the LAA of patients with atrial fibrillation would significantly reduce the incidence of stroke in those patients.
Pharmacological therapies for stroke prevention such as oral or systemic administration of warfarin or the like have been inadequate due to serious side effects of the medications and lack of patient compliance in taking the medication. Invasive surgical or thorascopic techniques have been used to obliterate the LAA, however, many patients are not suitable candidates for such surgical procedures due to a compromised condition or having previously undergone cardiac surgery. In addition, the perceived risks of even a thorascopic surgical procedure often outweigh the potential benefits. See Blackshear and Odell, above. See also Lindsay B D., Obliteration of the Left Atrial Appendage: A Concept Worth Testing, Ann Thorac. Surg., 1996.61(2):515.
Despite the various efforts in the prior art, there remains a need for a minimally invasive method and associated devices for reducing the risk of thrombus formation in the left atrial appendage.
Other conditions which would benefit from a tissue aperture closure catheter are tissue openings such as an atrial septal defect. In general, the heart is divided into four chambers, the two upper being the left and right atria and the two lower being the left and right ventricles. The atria are separated from each other by a muscular wall, the interatrial septum, and the ventricles by the interventricular septum.
Either congenitally or by acquisition, abnormal openings, holes or shunts can occur between the chambers of the heart or the great vessels (interatrial and interventricular septal defects or patent ductus arteriosus and aorthico-pulmonary window respectively), causing shunting of blood through the opening. The ductus arteriosus is the prenatal canal between the pulmonary artery and the aortic arch which normally closes soon after birth. The deformity is usually congenital, resulting from a failure of completion of the formation of the septum, or wall, between the two sides during fetal life when the heart forms from a folded tube into a four-chambered, two unit system.
These deformities can carry significant sequelae. For example, with an atrial septal defect, blood is shunted from the left atrium of the heart to the right, producing an over-load of the right heart. In addition to left-to-right shunts such as occur in patent ductus arteriosus from the aorta to the pulmonary artery, the left side of the heart has to work harder because some of the blood which it pumps will recirculate through the lungs instead of going out to the rest of the body. The ill effects of these lesions usually cause added strain on the heart with ultimate failure if not corrected.
Previous extracardiac (outside the heart) or intracardiac septal defects have required relatively extensive surgical techniques for correction. To date the most common method of closing intracardiac shunts, such as atrial-septal defects and ventricular-septal defects, entails the relatively drastic technique of open-heart surgery, requiring opening the chest or sternum and diverting the blood from the heart with the use of a cardiopulmonary bypass. The heart is then opened, the defect is sewn shut by direct suturing with or without a patch of synthetic material (usually of Dacron, Teflon, silk, nylon or pericardium), and then the heart is closed. The patient is then taken off the cardiopulmonary bypass machine, and then the chest is closed.
In place of direct suturing, closures of interauricular septal defects by means of a mechanical prosthesis have been disclosed.
U.S. Pat. No. 3,874,388 to King, et al. relates to a shunt defect closure system including a pair of opposed umbrella-like elements locked together in a face to face relationship and delivered by means of a catheter, whereby a defect is closed. U.S. Pat. No. 5,350,399 to Erlebacher, et al. relates to a percutaneous arterial puncture seal device also including a pair of opposed umbrella-like elements and an insertion tool.
U.S. Pat. No. 4,710,192 to Liotta, et al. relates to a vaulted diaphragm for occlusion in a descending thoracic aorta.
U.S. Pat. No. 5,108,420 to Marks relates to an aperture occlusion device consisting of a wire having an elongated configuration for delivery to the aperture, and a preprogrammed configuration including occlusion forming wire segments on each side of the aperture.
U.S. Pat. No. 4,007,743 to Blake relates to an opening mechanism for umbrella-like intravascular shunt defect closure device having foldable flat ring sections which extend between pivotable struts when the device is expanded and fold between the struts when the device is collapsed.
Notwithstanding the foregoing, there remains a need for a transluminal method and apparatus for correcting intracardiac septal defects, which enables a patch to placed across a septal defect to inhibit or prevent the flow of blood therethrough.
The present invention provides a closure catheter and methods for closing an opening in tissue, a body lumen, hollow organ or other body cavity. The catheter and methods of its use are useful in a variety of procedures, such as treating (closing) wounds and naturally or surgically created apertures or passageways. Applications include, but are not limited to, atrial septal defect closure, patent ductus arteriosis closure, aneurysm isolation and graft and/or bypass anostomosis procedures.
There is provided in accordance with one aspect of the present invention a method of closing an opening in a wall of the heart. The method comprises the steps of advancing a catheter through the opening, and deploying at least two suture ends from the catheter and into tissue adjacent the opening. The catheter is retracted from the opening, and the suture ends are drawn toward each other to reduce the size of the opening. The opening is thereafter secured in the reduced size.
In one embodiment, the advancing step comprises advancing the catheter through an atrial septal defect. The deploying step comprises deploying at least four suture ends. Preferably, each suture end is provided with a tissue anchor, and the deploying step comprises advancing the tissue anchors into tissue adjacent the opening. The securing step comprises knotting the sutures, clamping the sutures, adhesively bonding the sutures and/or the tissue to retain the opening in the reduced size.
In accordance with another aspect of the present invention, there is provided an atrial septal closure catheter. The catheter comprises an elongate flexible body, having a proximal end and a distal end, and a longitudinal axis extending therebetween. At least two supports are provided on the distal end, the supports moveable from a first position in which there are substantially parallel with the axis, and a second position in which they are inclined with respect to the axis. A control is provided on the proximal end for moving the supports from the first position to the second position. In one embodiment, the supports incline radially outwardly in the proximal direction when the supports are in the second position.
Preferably, the closure catheter comprises at least four supports, and each support carries at least one anchor. Each anchor is preferably provided with an anchor suture.
In accordance with a further aspect of the present invention, there is provided a method for closing an opening in a wall of the heart. The method comprises the steps of providing a catheter having at least three tissue anchors thereon, each tissue anchor having a suture secured thereto. The catheter is advanced to the opening in the wall of the heart, and the anchors are inclined outwardly from the axis of the catheter to aim the anchors at tissue surrounding the opening. The anchors are deployed into tissue surrounding the opening, and the sutures are manipulated to reduce the size of the openings.
In one embodiment, the deploying the anchors step comprises deploying the anchors in a proximal direction. In another embodiment, the deploying the anchors step comprises deploying the anchors in a distal direction.
In accordance with a further aspect of the present invention, there is provided a closure catheter for closing an atrial septal defect. The catheter comprises an elongate flexible tubular body, having a proximal end and a distal end, and a longitudinal axis extending therebetween. At least two anchor supports are provided on the distal end, the anchor supports moveable between an axial position in which they are substantially parallel with the longitudinal axis, and an inclined position in which they are inclined laterally away from the axis. A control is provided on the proximal end, for moving the anchor supports between the axial and the inclined positions. Each anchor support has a proximal end and a distal end, and the distal end is pivotably secured to the catheter so that the proximal end moves away from the axis when the anchor support is moved into the inclined position.
In one embodiment, the closure catheter further comprises an anchor in each of the anchor supports. Preferably, from about four to about 10 anchor supports are each provided with an anchor. Each anchor is preferably connected to a suture.
In one embodiment, a retention structure is removably carried by the distal end of the catheter or slideably carried by the suture. The retention structure is adapted to be distally advanced such that it constricts around the sutures, thereby securing them in a desired position. In one embodiment, the retention structure comprises a slideable knot, such as a Prusik knot.